Gates’ company wants to develop a molten-chloride prototype by 2030, and the laboratory will be used to test reactor materials in the meantime.

John Gilleland, the company’s chief technology officer, told Business Insider that molten chloride designs are the “ultimate green reactor”.

“It not only would allow you to produce electricity without carbon emissions, but by shipping the heat directly to some process in an industrial facility, you can provide the necessary heat to cause reactions to occur in industrial processing, or whatever you want to use it for, without carbon emissions,” Gilleland said.

How a molten-salt reactor works

Nuclear energy grew into prominence after 20th-century scientists figured out how to harness the atom’s power, but high costs and safety concerns over dangerous radioactive waste have deterred many countries from investing in it.

Nuclear energy is produced when radioactive fuel is put into a reactor to trigger fission – a process in which the nucleus of an atom splits within a reactor core.

In light-water reactors, solid fuel sits within cladding, or corrosion-resistant metal that prevents radioactive pieces from contaminating the coolant. The water around the cladding helps turn a reaction’s heat into steam for turbines, which generate electricity.

TerraPower’s liquid-chloride design, however, puts uranium fuel and the coolant in the same molten salt, Gilleland said.

Fission can heat the salts directly as the mixture flows through the reactor core, and the mixture then goes through heat exchangers to generate heat or electricity, he said.

Light-water reactors can’t sustain reactions at very high temperatures because the coolant evaporates. With molten chloride, though, TerraPower could operate reactors at much higher temperatures than before.

In addition to generating electricity, nuclear technology could be used in high-temperature processes like fertiliser production and oil refining.

The materials inside light-water reactors degrade quickly and need to be replaced roughly every 18 months, as it becomes more difficult to sustain fission with older fuel.

Molten-chloride reactors, meanwhile, produce little residual waste and could theoretically run for years without the need to add fuel or get rid of waste.

TerraPower’s design is also less likely to be used in nuclear-weapon production because its radioactive fuel is not isolated.

TerraPower’s new reactor was inspired by a 1960s experiment

Though TerraPower began working on its newest line of reactors just a few years ago, the design is based on Cold War-era molten-salt technology. (TerraPower has also spent the past decade developing a travelling-wave reactor, another advanced design.)

Researchers at the Oak Ridge National Laboratory in Tennessee developed a molten-salt reactor in the 1960s, but funding came to a halt several years later as scientists raised concerns about corrosion and safety problems associated with the reactor.

Now, with government funding and the support of billionaires like Gates, these reactors have another shot at hitting the market.

TerraPower and Southern Company are working on their design with scientists from Oak Ridge National Laboratory, Idaho National Laboratory, the Electric Power Research Institute, and Vanderbilt University.

Several other startups are competing with Gates’ company to commercialize similar molten-salt reactors.

In April, Florida-based company ThorCon received US$400,000 from the US Department of Energy for a joint research project with Argonne National Laboratory.

In a blog post announcing the shutdown, Transatomic CEO Leslie Dewan acknowledged there had been errors in early analyses and said the company was unable to scale up fast enough.

Transatomic Power later open-sourced its intellectual property for other researchers to use.

Clean energy is in urgent demand, and Gates’ startup is at least a decade away from a working prototype

Renewable energy use is growing too slowly to prevent dangerous climate change on its own.

If governments don’t implement new policies that reduce carbon-dioxide emissions, the bulk of the world’s energy will still come from fossil fuels, according to the International Energy Agency’s 2018 World Energy Outlook.

Solar, wind, and nuclear-energy systems are not keeping up with global energy demands, the report said.

About 25 percent of the world’s electricity comes from renewable energy sources, according to the World Energy Outlook.

The International Energy Agency predicts that the share will rise to 40 percent by 2040, and nuclear energy can prove to be a vital factor in any changes.

For Southern Company and TerraPower, the companies’ ambitious plan could produce a new reactor well before 2040.